OBJECTIVE: Cancer metastasis is a complex process involving a sequential series of multi-step genetic events, which produces an imbalance between stimulatory and inhibitory genes for metastasis. Presently, we examined the expression of metastatic tumor antigen 1 (MTA1) and nonmetastatic protein 23 homologue H1 (nm23-H1) proteins in metastasized epithelial ovarian cancer cells. METHODS: Fifty-one primary epithelial ovarian tumors and corresponding lymph nodes (LNs) were examined immunohistochemically for expression of MTA1 and nm23-H1. Expression of these proteins was statistically evaluated. RESULTS: The frequency of MTA1 expression was 30.3% (10/33) in stage III/IV LNs but was absent (0/18) in stage I/II LNs (p=0.01). MTA1 expression was observed in 50% (6/12) of metastasizing LNs but in only 10.3% (4/39) of non-metastasizing LNs (p=0.01). In contrast with MTA1, nm23-H1 expression was evident in 16 of 18 (88.9%) stage I/II ovarian cancer tissue samples but only in 20 of 33 (60.6%) stage III/IV tissues (p=0.05), and nm23-H1 production was also observed in 75.6% (34/45) of ovarian cancer tissue with residual tumors under 2 cm in diameter, but in 2/6 (33.3%) of cancer tissue with residual tumors exceeding 2 cm in diameter (p=0.03). CONCLUSION: The degree of expression and imbalance of MTA1 and nm23H1 are correlated with ovarian cancer LN metastasis.